1. Field of the Invention
This invention relates to a solid-state image pick-up apparatus using a solid-state image sensor such as a CCD image sensor, etc. formed by CCDs (Charge Coupled Devices), and more particularly to a solid-state image pick-up apparatus provided with a solid-state image sensor of the frame interline transfer type, which is adapted to transfer, to a storage section through vertical transfer registers, image pick-up charges obtained by photosensitive elements of the odd rows and photosensitive elements of the even rows arranged in a matrix form, which constitute an image sensing (image pick-up) section, thus to line-sequentially output those image pickup charges through a horizontal transfer register from the storage section.
2. Description of the Prior Art
Generally, in a solid-state image sensor having a discrete pixel structure where a plurality of photosensitive elements are arranged in a matrix form, in order to cope with the interlaced scanning system employed in an ordinary television system, photosensitive elements 21 of the odd rows and photosensitive elements 22 of the even rows are alternately arranged in a vertical direction in respective columns of the matrix as shown in FIG. 5, for example, thus to line-sequentially output image pickup charges obtained in the frame storage mode or the field storage mode.
In the above-mentioned frame storage (accumulating) mode, as shown in FIG. 6, image pick-up charges S.sub.O, S.sub.E are respectively accumulated within every one frame period in the states shifted to each other by one field period by photosensitive elements 21, 22 of the odd and even rows corresponding to pixels of respective fields to interchangeably read out, to vertical transfer registers 23 every field during a vertical blanking period, image pick-up charges S.sub.O by the photosensitive elements 21 of the odd rows and image pick-up charges S.sub.E by the photosensitive elements 22 of the even rows shown in FIG. 5 to line-sequentially output those image pick-up charges through a horizontal transfer register 24. On the other hand, in the field storage (accumulating) mode, as shown in FIG. 7, image pick-up charges S.sub.O, S.sub.E are respectively accumulated within every one field period by photosensitive elements 21, 22 of the odd and even rows corresponding to pixels of respective fields to read out, to the respective vertical transfer registers 23, image pick-up charges S.sub.O by the photosensitive elements 21 of the odd rows and image pick-up charges S.sub.E by the photosensitive elements 22 of the even rows in the state where combinations of image pick-up charges by photosensitive elements adjacent in upper and lower directions are changed so that respective image pick-up charges are mixed every field during a vertical blanking period to line-sequentially output them through the horizontal transfer register 24.
Namely, a solid-state image sensor operative in the frame accumulating mode carries out an image pick-up operation such that one frame period, i.e., 1/30 seconds in the case of the NTSC system (1/25 seconds in the case of the PAL system) is used as an exposure period (shutter speed). On the other hand, a solid-state image sensor operative in the field accumulating mode carries out an image pick-up operation such that one field period, i.e., 1/60 seconds in the case of the NTSC system (1/50 seconds in the case of the PAL system) is used as the exposure period (shutter speed).
The solid-state image sensor 20 shown in FIG. 5 is of the structure to line-sequentially output image pick-up charges obtained by the photosensitive elements 21, 22 through the horizontal transfer register 24 from the vertical transfer registers 23, and is known as an interline transfer type solid-state image sensor. Further, there have been conventionally known as the solid-state image sensor, in addition to the above-mentioned interline transfer type solid-state image sensor, a frame transfer type CCD image sensor in which e.g., vertical transfer registers by CCDs are provided at the portions of the photosensitive elements, and a storage (accumulating) section comprised of vertical transfer registers by CCDs is provided on the terminating side of the above-mentioned vertical transfer registers, thus to line-sequentially output image pick-up charges through the horizontal transfer register from the storage (accumulating) section; a frame interline transfer type solid-state image sensor provided with a storage (accumulating) section between the vertical transfer registers and the horizontal transfer register in the above-mentioned interline transfer type solid-state image sensor, and the like.
Further, in a solid-state image sensor such as a CCD image sensor, etc., there has been conventionally known an electronic shutter function to sweep out image pick-up charges produced in the photosensitive elements into, e.g., an overflow drain to thereby control the effective charge accumulating period (exposure period). The above-mentioned electronic shutter function is realized by controlling an overflow drain potential by a voltage (shutter pulse) applied to the substrate.
Meanwhile, in a conventional solid-state image pick-up apparatus using a CCD image sensor having an electric function, in the case where an attempt is made to control the exposure period by the above-mentioned electronic shutter, there are the problems described below. Namely, in a solid-state image sensor operative in the field accumulating mode, the exposure period can be controlled only within one field period in principle. On the other hand, even in a solid-state image sensor operative in the frame accumulating mode, image pick-up charges S.sub.O, S.sub.E obtained by photosensitive elements corresponding to pixels of the first field and photosensitive elements of the even rows corresponding to pixels of the second field are both swept out into the overflow drain by applying a shutter pulse to the substrate. For this reason, even in the case of such solid-state image sensor operative in the frame accumulating mode, there was the problem that the exposure period is only permitted to be controlled solely within one field period.